How popular is Cydney?

Cydney is a rare first name for females. Cydney is an equally unique last name for all people. (2000 U.S. Demographics)

Cydney entered the list in 1950-1959 and reached its highest rank of #915 in the U.S. in 1997, but is not found in the list currently. (Top 2000 Names, 2015)

Which version is better?

with its variant forms and related girl names. Sidney(#999 from recent data), Sydnee, Sydney(#122), Sydni and Sydnie are the popular varying forms of Cydney. Usage of these relations of Cydney was well-received among parents 2 decades ago (average #502) and has become significantly lower since (#1520, 80.4% less usage), with forms like Sydnee becoming less in vogue.